The Company’s 2008 Equity Incentive Plan (the “2008 Plan”) provided for the grant of incentive stock options, non-statutory stock options, restricted stock awards and restricted stock units to employees and non-employee service providers of the Company. Under the 2008 Plan, the exercise price of stock options granted were at 100% of the estimated fair market value of the Company’s common stock on the date of grant and the contractual term of stock options granted were between five and ten years. Options become vested and, if applicable, exercisable based on terms determined by the Company’s board of directors or other plan administrator on the date of grant, which is continued employment or service as defined in each option agreement.

In 2018, the 2008 Plan expired and 86,000 stock options granted prior to the 2008 Plan expiration remain outstanding as of June 30, 2024.

The Company’s 2010 Equity Incentive Plan (the “2010 Plan”) provided for the grant of incentive stock option, non-statutory stock options, stock appreciation rights, restricted stock awards and restricted stock unit awards to employees and non-employee service providers of the Company. Under the 2010 Plan, the exercise price of stock options granted were at 100% of the estimated fair market value of the Company’s common stock on the date of grant and the contractual term of stock options granted did not exceed ten years. Options become vested and, if applicable, exercisable based on terms determined by the Company’s board of directors or other plan administrator on the date of grant, which is continued employment or service as defined in each option agreement. Stock appreciation rights (“SARs”) provide a participant with the right to receive the aggregate appreciation in stock price over the market price of the Company’s common stock at the date of grant, payable in cash. The rights granted have varying vesting terms, including SARs that vest immediately on the grant date and upon satisfaction of the service-based requirement, typically three to five years. The maximum fair value is limited to four times the exercise price.

In February 2020, the 2010 Plan expired and 102,000 stock options granted prior to the expiration remain outstanding as of June 30, 2024.

The Company’s 2020 Equity Incentive Plan (the “2020 Plan”) authorizes the grant of equity awards for up to 206,000 shares of the Company’s voting common stock and 206,000 of the Company’s non-voting common stock.

The 2020 Plan provides for the grant of incentive stock options, non-statutory stock options and restricted stock to employees and non-employee service providers. Under the 2020 Plan, the contractual term of stock options shall not exceed ten years and the exercise price of stock options granted shall not be less than 100% of the estimated fair market value of the Company’s common stock on the date of grant. However, the exercise price of incentive stock options granted to a 10% stockholder shall not be less than 110% of the fair market value of the common stock on the date of grant and the contractual term shall not exceed ten years. Options become vested and, if applicable, exercisable based on terms determined by the Company’s board of directors or other plan administrator on the date of grant, which is continued employment or service as defined in each option agreement. Restricted stock has vesting terms that vest immediately on the grant date or upon satisfaction of the service-based requirement, typically four years or the performance-based requirement. The Company has a repurchase right exercisable upon termination of continuous service with respect to restricted stock for any shares that are issued and unvested.

In December 2022, the 2020 Plan expired and 190,000 stock options and 2,000 RSUs granted prior to the 2020 Plan expiration remain outstanding as of June 30, 2024.

In December 2022, the Company approved the 2022 Equity Incentive Plan (the “2022 Plan”). The 2022 Plan provides for the grant of incentive stock option, non-statutory stock options, restricted stock, restricted stock units, stock appreciation rights (“SARs”), performance units and performance shares to employees, directors and independent contractors of the Company. Under the 2022 Plan, the exercise price of stock options grants shall be at 100% fair market value of the Company’s common stock on the date of grant and the contractual term of stock options granted shall not exceed ten years. Options become vested and, if applicable, exercisable based on terms determined by the Company’s board of directors or other plan administrator on the date of grant, which is continued employment or service as defined in each option agreement. SARs provide a participant with the right to receive the aggregate appreciation in stock price over the market price of the Company’s common stock at the date of grant, payable in cash or in shares of equivalent value.

The following table summarizes stock option activity under the Company’s equity incentive plans:


	Outstanding Stock Options			Weighted-Average Exercise Price Per Share		Weighted-Average Remaining Contractual Term (years)		Aggregate Intrinsic Value
	(in thousands, except per share amounts and years)
December 31, 2023		1,975		$	9.00		7.6	$	604
Granted		940		$	0.36
Exercised		—		$	—
Forfeited		(296	)	$	8.83
Expired		(165	)	$	11.39
Outstanding as of June 30, 2024		2,454		$	5.55		8.7	$	160
Exercisable as of June 30, 2024		1,378		$	8.40		8.2	$	63

On April 11, 2024, the Compensation Committee of the Board approved and on April 14, 2024, the Board approved and adopted the Annual Stock Awards and Employee Retention Policy (the “Policy”), which will provide retention awards to key employees, including certain of the Company’s named executive officers. Under the Policy, the Company’s former Chief Executive Officer and the Company’s Chair of the Board, Shawn Iadonato, Ph.D., the Company’s President, Craig W. Philips, the Company’s Chief Financial Officer, Keith A. Baker, and the Company’s Chief Scientific Officer, Thierry Guillaudeux, Ph.D., received option awards to purchase 225,000, 225,000, 225,000 and 225,000 shares of the Company’s common stock, respectively. The awards are subject to three-part vesting: (i) 25% of the shares will vest upon award; (ii) 50% of shares will vest in the event of a Transaction or a Qualified Transaction, as such terms are defined in the Policy; and (iii) 25% of the shares will vest and become exercisable over the 36-month period following the award on the one-month anniversary of the vesting commencement date, subject to the optionee’s continued service through each vesting date.

The fair value of stock options granted for employee and non-employee awards was estimated at the grant date using the Black-Scholes option pricing model based on the following assumptions:


	Six Months Ended June 30,
	2024	2023
Expected volatility	121.8%	110.3% - 111.6%
Expected term (years)	1.0	6.5
Risk-free interest rate	5.07%	3.4% - 3.4%
Expected dividend yield	0% - 0%	0% - 0%

The Company has granted restricted stock units (“RSUs”) under its equity incentive plans with both service-based and performance-based vesting conditions. As of June 30, 2024, the Company’s outstanding RSUs are time-based and have a grant date fair value of $63,000.

The following table summarizes the Company’s restricted stock activity consisting of RSUs:


	Number of Restricted Stock (RSUs)			Weighted-Average Grant Date Fair Value Per Share

Outstanding and unvested as of December 31, 2023		7,516		$	27.14
Exercised/Released		(4,191	)	$	27.20
Cancelled/Forfeited		(1,032	)	$	26.16
Outstanding and unvested as of June 30, 2024		2,293		$	27.47

The following table summarizes total stock-based compensation included in the Company’s consolidated statements of operations:


	Three Months Ended June 30,				Six Months Ended June 30,
	2024		2023		2024		2023
	(in thousands)
Research and development	$	84	$	348	$	158	$	425
General and administrative		285		1,522		688		2,499
Total stock-based compensation	$	369	$	1,870	$	846	$	2,924

As of June 30, 2024, there was $1.4 million of unrecognized stock-based compensation related to stock options and RSUs outstanding, which is expected to be recognized over a weighted-average remaining service period of 1.4 years.